HONEYSUCKLE WITCHES' BROOM APHID Jeffrey Hahn, Entomology Educator John F. Kyhl, Entomology Technician

The honeysuckle witches' broom aphid (Hyadaphis tataricae) was first found in Minnesota in 1981. This aphid species feeds on many common honeysuckle species and varieties and is probably the most damaging arthropod pest of this shrub. These aphids are very small (2 mm), light green to cream in color, and covered with fine, powdery wax. They overwinter as eggs in the branch tips of the honeysuckle, and hatch in early May in central Minnesota. The aphids feed on buds at first, but as the honeysuckle leafs out, move to the new leaves and feed along midveins. In spring and early summer, aphids give birth to live young. After several generations, wingless females and winged males are produced. They mate in late summer and early fall and produce egg laying females that disperse.

Fig. 1

Fig 2.

Honeysuckle witches' broom aphid feeding causes two main types of damage. First, their feeding causes leaflets to distort, fold up, and cover the aphids (Fig.1). The folded leaflets protect the aphids from hard rains, heavy winds, predaceous insects, and contact insecticides. The second type of damage is the formation of distinctive, stunted, abnormal growths called witches' brooms (Fig.2). Feeding slows branch growth, triggering dormant buds along the branch to open and grow. Numerous buds along a branch grow simultaneously, giving a bushy or broom-like appearance. At first, only the appearance of the shrub is affected, but continued feeding over a period of years often stunts the honeysuckle's growth, eventually weakening it and contributing to the shrub's death.

Honeysuckle witches' broom aphid is a difficult pest to manage. Susceptible honeysuckle varieties have become high maintenance shrubs, requiring considerable time and effort to maintain their health and appearance. A proper pest management program must be maintained all season, every year. While proper management can greatly reduce honeysuckle witches' broom aphid injury, some aphids and damage will probably be present each year.

The best long term solution is to remove unattractive, heavily damaged, susceptible shrubs. Replace them with other types of plantings (e.g. flower beds or shade gardens), other species of shrubs (e.g. highbush cranberry or witch hazel), or with honeysuckle varieties that are resistant to honeysuckle witches' broom aphid. When replanting with honeysuckle, avoid planting 'Tartarian', 'Zabel', and other varieties that are susceptible to honeysuckle witches' broom aphid. Instead, select resistant varieties, such as 'Freedom', 'Honeyrose', 'Arnold's Red', 'Clavey's Dwarf', 'Miniglobe', 'Emerald Mound', and 'Sakhalin honeysuckle'. These varieties are available from many nurseries and garden centers.

If susceptible honeysuckle shrubs are established in the landscape, pruning and insecticide applications can minimize damage to susceptible shrubs in the short term. Pruning will help manage aphids in some situations and not in others. While pruning removes eggs and generally improves appearance of a shrub, it is effective only if the plants are isolated. Pruning is of little benefit if the shrub is part of a large planting, or if there are many untreated and unpruned plants nearby, because the likelihood of re- infestation by winged females from nearby plants is high. Pruning honeysuckle shrubs also prompts the production of more vegetative buds. Since the honeysuckle witches broom aphid prefers vegetative buds over floral buds, it is more likely to feed on recently pruned than unpruned shrubs. If you prune, look for witches' brooms during winter when they are easiest to see. Prune out and destroy all infested branches at least six inches below the witches' broom before budbreak to remove overwintering eggs.

You can supplement your non-chemical management efforts with insecticide applications. Two insecticides that are effective against honeysuckle witches' broom aphid are acephate (e.g. Orthene) and dimethoate (e.g. Cygon). Apply either insecticide 3-5 times during the growing season. Three applications (June 1, July 1, and August 1) will generally keep the shrub healthy, but will not completely control the aphids. Five applications (late May, mid June, mid July, early August, and early September) should keep the shrub healthy and minimize abnormal growth.

CAUTION: Read all label directions very carefully before purchasing and again before using. Information on the label should be used as the final authority.

If honeysuckle witches' broom aphid is a problem that you don't want to attempt to treat yourself, or have been unable to successfully treat this problem in the past, consider contacting a reputable landscape care service. They have experience treating tree and shrub pests, and have an array of equipment and chemicals that are unavailable to most homeowners. Given the difficulty in controlling this pest, good results are not guaranteed; successful management is difficult for anyone to achieve, regardless of experience and chemicals used.

E451H
Revised 2/99